Update the CHANGELOG.md to be consistent with the Flutter IJ format

https://keepachangelog.com/en/1.0.0/

Author: jwren

third_party/CHANGELOG.md

@@ -1,14 +1,30 @@
-# Dart Plugin for IntelliJ Changelog
+## Unreleased
 
-## [Unreleased]
+### Added
+
+### Removed
+
+- "Scope analysis to the current package" feature from the Dart problem view
+- Code Coverage support, all references to com.intellij.coverage.*
+- Dart embedded in HTML support
+
+### Changed
 
  - Vendor change from "JetBrains" to "Google"
  - Build system change from Basel to Gradle
- - Removal of the old Code Coverage support, all references to com.intellij.coverage.*
- - Removal of the Dart embedded in HTML support
- - Remove the "Scope analysis to the current package" feature from the Dart problem view
+
+
+## 251.27812.12
+
+### Added
+
  - New Dart language feature: Dot Shorthands (https://youtrack.jetbrains.com/issue/IDEA-370100)
  - Support new 'Null-Aware Elements’ syntax (https://youtrack.jetbrains.com/issue/IDEA-374053)
+
+### Removed
+
+### Changed
+
  - Fix: IDE freezes after inserting a piece of Dart code (https://youtrack.jetbrains.com/issue/IDEA-231468)
  - Fix: DartParser performance issue: sluggish typing in the editor (https://youtrack.jetbrains.com/issue/IDEA-365957)
  - Fix: Format of very long line gives uncompilable code (https://youtrack.jetbrains.com/issue/IDEA-328345)